The present invention relates to high voltage semiconductor devices, and more particularly to such devices that are electrically isolated from an integrated circuit substrate as well as from each other.
The above-referenced Adler application discloses and claims a high voltage semiconductor device, described in detail below, that is capable of forward conducting a high voltage while maintaining electrical isolation from an integrated circuit substrate on which it is constructed. The Adler device includes a field gate electrode, referenced to a selected potential, which operates in combination with a buried layer to pinch off an inherent MOSFET when the device is in a reverse blocking mode of operation. This pinching off of the MOSFET functions to reduce the potential of the buried layer when the device is in this reverse blocking mode of operation, thereby inhibiting avalanche breakdown of certain reverse-biased, bipolar junctions.
The present inventors have discovered that, with appropriate biasing of the field gate electrode, in the reverse blocking mode of operation the buried layer in the Adler device rises to a potential of approximately 60 volts. It would be desirable to provide a high voltage semiconductor device of the same type as the Adler device but having a reduced pinch-off voltage of the inherent MOSFET. Such a device would provide all the benefits of the Adler device while offering greater reliability of operation over an increased lifespan.